function checkBrowser(){
	this.ver=navigator.appVersion
    var agt=navigator.userAgent.toLowerCase();

	this.dom=document.getElementById?1:0
	this.ie5=(this.ver.indexOf("MSIE 5")>-1 && this.dom)?1:0;
	this.ie4=(document.all && !this.dom)?1:0;
	this.opera=(document.all && agt.indexOf("opera")>0)?1:0
	this.ns5=(this.dom && parseInt(this.ver) >= 5) ?1:0;
	this.ns4=(document.layers && !this.dom)?1:0;
	this.bw=(this.ie5 || this.ie4 || this.ns4 || this.ns5)
    this.mac    = (agt.indexOf("mac")!=-1);

	return this
}
bw=new checkBrowser()